The invention relates to an ultrasonic imaging apparatus operating according to the impulse-echo method, particularly for medical diagnostics, with an ultrasonic applicator for linear ultrasonic scanning of an examination subject and an image display device with a line generator for reproducing the echo pulses as lines and also an image generator for displacement of lines as a function of the displacement of the ultrasonic beam in the subject, there being inserted between the image display device and the ultrasonic applicator a controllable electronic receiving gate which allows only echo pulses from an adjustable depth of field of the examination subject to pass through to the image display device.
Ultrasonic imaging apparatus with electronic receiving gates for limiting the zone of representation of echo signals are previously known, for example, from the German Offenlegungsschrift Nos. 1,928,366 and 2,060,260. In these video apparatus, however, in the case of an ultrasonic scanning process line-by-line in parallel superposed planes, the problem consists of obtaining echo impulses only from those planes or curved surfaces of the examination subject which lie substantially vertical to the direction of irradiation of the ultrasound into the examination subject, i.e. vertical to the scanned planes. For this purpose, the receiving gate has to be adjusted to relatively narrow receiving, such adjustment of the gate corresponding to the transmission of echo signals produced by a given ultrasonic pulse within a relatively narrow time interval corresponding to a relatively narrow depth range where depth is taken in the direction of propagation of the ultrasonic energy. However, independently thereof, the problem which also frequently arises in ultrasonic sectional image diagnostics consists in that a limitation of range must be effected within the plane scanned by the ultrasonic beam, such that echo impulses from only a limited depth range in the scanning plane are received and represented on the display device. It is thus possible to block out those parts of the ultrasonic sectional image which are not of interest from the image representation so that only the parts actually of interest are presented to the viewer.